The BLTouch is more accurate when probing in "pin_down" mode than
"touch_mode" (at least on some hardware). Rework the code to use that
mode.
When probing in pin_down mode, the BLTouch can go into an error state
if a pin_up is not sent immediately after a touch signal. Rework the
pin_up code to reduce the time it takes to transmit the command.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>